Controlling induction-motors.



R. VAN -R. SILL.

CONTROLLING moucnou morons.

-' APPLICATION mm FEB. 3. 1914. 1,245,993.

Patented Nov. 6, 1917- 7% Wig-i986: WEE/2i? M ,4 A: @f 7ZLA B %ZATTORNEY UNITED STATES PATENT OFFICE.

arcrmnn VAN RENSSELAEB SILL, or NEW YORK, N. Y., .ASSIGNOB. or oNn-rnmn'ro 'mnoNzo E. IELHAM AND ONEPTHIBD 'ro em'roN L. main, or NEW Yonx, N.Y.

CONTROLLING INDUCTION -MOTOBS.

Leases.

1'0 all whom it may concern: .Be it known that I RICHARD VAN R. Sum; ofthe city of New York, in the county New York and State of New York, haveinvented-certain new and useful Improvements in ControllingInduction-Motors; and I do hereby declare the following to be a full,clear, and exact description of the invention,

.10 to which it appertains to make and use the same.

In order to properly control polyphase nduction motors, it is desirablethat in cutting out the resistance the speed should be increaseduniformly and not in jerks or it ar jumps.

' en the clrcuits for each phase are balaimed,- that is, the resistorsin circuit with the several phases are equal, it is usual to have thefirst section of each resistor of eater resistance than the followingsec- .ions. When these sections are cut out suc- (eessively, the s eedincreases varyingly, that is, hot uniform y. The first section being ofunequal resistance relatively to the next-two,

the speed increase is not as greatin proportion'when the first sectionis cut out as when the second is cut out, and likewise, not as t whenthe second is cut out as when the 3,0 t ird is cut out. When the fourthsection is put out the resistance of the different sections less thanthat of the former sections, there a jum in the speed oi the motor. Thisrenders a ternating current motors as $5 heretofore constructedunavailable for certain kinds of work, such as hoists for elevatinandsetting girders and stone and on at es where variable speeds arerequired.

' I have overcome this difliculty by maintainin the resistances incircuit with the severe phase windings unbalanced throughout the periodof acceleration. In other ,words all the circuits have not the samedegree of resistance. The phase windings are $5. continuously connectedto their resistances and I shift the resistance from one phase circuitto another.

.?1he accompanying drawing shows a diarammatic sketch of a method ofcontrol em- Sid odymg my invention. 1 represents'the resistance as anentirety, the parts thereof being designated by the numerals 2, 3 and 4,each oi which is shown connected to a phase winding of the rotor 5. At 6I have indirated a switch in the iorm of a five point Specification ofLetters 1atent.'

such as will enable others skilled in the art- At this time the currentis from part 4 'contact while B and 'R are stillin circuit.

Patented Nov. 6, 1917.

Application med February a, 1914. Serial No. 816,228.

. to left. When it is thrown on the first notch La and S and L and S areconnected and the flow of the current is from G through La and S to thepoint S on the stator and from I through L and S to S on the stator andback through neutral N to H, thus supplying the full line voltage to theprimary or stator.

At this time the induced current set up in the rotor flows through theconductors a, b and 0, respectively, to resistance parts 2, 3 and 4. Ihave shown these parts of the resistance in Y connection by theconductors M, N, whereby the current passin through c to 4 may continuethrough M an N to parts 3 and 2, and the same is true of the currentpassing throu h conductors a and b to parts 2 and 3 of t e resistance.

It will be noted that resistance part 2 is of less ohmic value thanparts 3 and 4, and

- consequently is always unbalanced relatively to those parts during theoperation of the. switch.

On moving controller 6 to the second notch R and R are connected. Thisshort circuits parts 3 and 4 at R" and R thus cutting out one of thesections of each of these parts and connecting the resistance parts inparallel and in series with part 2.

through R, R, R and R" of part 3 and entirely through part 2 over M andN -tof3 an 4.

On the third notch R is brought into R is connected with point It" onresistance part2. At this time the flow of the current is through parts3and 4, as described with reiference to the second'notch, and to R ofpart 2, cuttin out a seetionof this part.

'Onjthe fou h notch It and R are con- .nected- 'hind R is connected withR, cutting.

, out another section of parts 3 and 4. The

resistance remaining below the parts R, It, Rfl iafter the switch hasbeen fully turned on to the fifth point, constitutes a permanentsecondary resistance which may be maintained in the motor.

I claim as my invention:

1. In a polyphase induction motor having phase windings always incircuit, a resistance in circuit with each phase winding, a switch forcontrolling said resistance parts, and means for constantly maintainingsaid resistance parts relatively unequal or unbalanced in the operationof said switch.

2. In a polyphase induction motor having phase windings always incircuit, a resistance in circuit with each phase winding, all of saidcircuits not having the same degree of resistance, a switch for cuttingout said several resistances, and conductors leading from each of saidresistance parts to points on said switch to maintain the inequality ofsaid resistance partsirom the first notch throughout the operation ofsaid switch.

3. In a polyphase induction motor, the combination with the rotor and aswitch, of a plurality of resistance parts each in circuit with a phasewinding of the rotor, said parts being of unequal ohmic values, and

means operated. by said switch for cutting out sections of a pluralityof parts on a predetermined notch while maintaining the full resistanceof another resistance part.

4. In a polyphase induction motor, the combination with a switch, of aplurality of resistance parts connected together in series and each ofsaid parts connected to a phase winding of the rotor, said parts beingof difierent ohmic values, and means rendered effective at apredetermined notch of said controller for connecting said resistanceparts in parallel.

5. In a polyphase induction motor having phase windings, a resistance incircuit with each phase winding of the rotor, a switch for controllingsaid resistance parts, and means for shifting the resistance from onephase circuit to another.

In testimony whereof, I have signed this specification in the presenceof two subscribing witnesses.

RICHARD VAN RENSSELAER SILL.

Witnesses:

GRAFTON L. MoGILL, MARION I. BALFoUR.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner 01'. Patents,

' Washington, .D. G."

